MPIX_Comm_failure_get_acked(3)

💖 MPIX_Comm_failure_get_acked 💖

okay bestie, this one lives in the MPI manual, section 3, and its full glow-up name is MPIX_Comm_failure_get_acked(3). let's get into it 🫶

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✨ NAME ✨

MPIX_Comm_failure_get_acked — get the group of acknowledged failures.

🌸 SYNOPSIS 🌸

int MPIX_Comm_failure_get_acked(MPI_Comm comm, MPI_Group *failedgrp)

💅 INPUT PARAMETERS 💅

• comm — communicator (handle)

🎀 OUTPUT PARAMETERS 🎀

• failedgrp — group of failed processes (handle)

🦋 NOTES 🦋

so this is a local operation, meaning it doesn't go chat with anybody else, it just tells you what you already know. it returns the group failedgrp of processes, out of the communicator comm, that have been locally acknowledged as failed by preceding calls to MPIX_Comm_failure_ack. 💀

and lowkey important: failedgrp can be empty — like, literally equal to MPI_GROUP_EMPTY. that's not a bug, bestie, that's just a valid vibe. 🫶

🔥 THREAD AND INTERRUPT SAFETY 🔥

this routine is thread-safe, periodt. that means you can safely use it from multiple threads and you do not need any user-provided thread locks. no gatekeeping, it handles itself. ✨

however — and this is the part where you listen — the routine is not interrupt safe. typically that's because of memory allocation routines like malloc or other non-MPICH runtime routines that are themselves not interrupt-safe. so yeah, not interrupt safe, noted, moving on. 😭

🌈 NOTES FOR FORTRAN 🌈

all MPI routines in Fortran (except for MPI_WTIME and MPI_WTICK) have an additional argument ierr at the end of the argument list. ierr is an integer and has the same meaning as the return value of the routine in C. in Fortran, MPI routines are subroutines, and they're invoked with the call statement.

all MPI objects (e.g., MPI_Datatype, MPI_Comm) are of type INTEGER in Fortran. iykyk 💜

💀 ERRORS 💀

all MPI routines (except MPI_Wtime and MPI_Wtick) return an error value; C routines as the value of the function, and Fortran routines in the last argument. before the value is returned, the current MPI error handler is called. by default, this error handler aborts the MPI job. 😳

the error handler may be changed with MPI_Comm_set_errhandler (for communicators), MPI_File_set_errhandler (for files), and MPI_Win_set_errhandler (for RMA windows). the MPI-1 routine MPI_Errhandler_set may be used but its use is deprecated 🙈 — like, it works, but don't make it your whole personality.

the predefined error handler MPI_ERRORS_RETURN may be used to cause error values to be returned. note that MPI does not guarantee that an MPI program can continue past an error; however, MPI implementations will attempt to continue whenever possible. best effort energy, fr fr. 🫶

• MPI_SUCCESS — no error; MPI routine completed successfully. slay ✨
• MPI_ERR_ARG — invalid argument. some argument is invalid and is not identified by a specific error class (e.g., MPI_ERR_RANK).
• MPI_ERR_COMM — invalid communicator. a common error is to use a null communicator in a call (not even allowed in MPI_Comm_rank). 🚫
• MPI_ERR_OTHER — other error; use MPI_Error_string to get more information about this error code.

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okay that's the whole page, you ate that 💅 this little legend was served up from the MPICH source, version stamped 4/10/2026, and it answers to the name MPIX_Comm_failure_get_acked(3). go forth and check your failure groups, bestie 🌟👑